Method of setting reserved subframes for resource pool, user equipment, and base station

ABSTRACT

The present disclosure provides a method of setting reserved subframes for indication of a resource pool by a bitmap, a user equipment, and a base station. In the present disclosure, the resource pool is used for transmitting or receiving sidelink signals within a system frame number cycle that includes predefined subframes and remaining subframes that are subframes after excluding the predefined subframes within the system frame number cycle. In the method, a number of the reserved subframes is determined so that the bitmap is repeated by integer times within the subframes after excluding the reserved subframes and the predefined subframes within the system frame number cycle. In the method, position of each of the reserved subframes is set, wherein at most two reserved subframes are set per n subframes within the system frame number cycle.

TECHNICAL FIELD

The present disclosure relates to a method of setting reserved subframesfor indication of a resource pool used for transmitting and/or receivingsidelink signals in the V2V/V2X communication system, and userequipment, as well as base station therefor.

BACKGROUND ART

Currently V2V (vehicle to vehicle)/V2X (vehicle to everything) resourcepool which is used for transmitting and/or receiving sidelink signalsconsists of certain resources in time and frequency domains, and theresource positions in the time domain are indicated by a bitmap. If acertain bit of the bitmap indicates “1”, it means that it is a V2V/V2Xsubframe, otherwise if a certain bit of the bitmap indicates “0”, itmeans that it is not a V2V/V2X subframe.

Based on current agreement of 3GPP (the 3rd Generation PartnershipProject), the size of the bitmap can be 16, 20 or 100 bits. Which bitmapsize is used in the communication could be configured or preconfigured.Based on current agreement of 3GPP, some subframes such as the subframestransmitting sidelink synchronization signal (SLSS) should be excludedfor the resource pool, and the bitmap may not be repeated by integertimes within the remaining subframes (after excluding SLSS subframes)within the system frame number (SFN/DFN) cycle. For example, it isassumed that there are 10240 subframes within a SFN cycle, and a SLSSsubframe is transmitted per 160 ms so there are 64 SLSS subframes withinthe SFN cycle, the number of the remaining subframes are 10240−64=10176,which cannot be divided by the size of the bitmap such as 20 bits or 100bits. There would be some resource collision problems in case that theremaining subframes cannot be divided by the size of the bitmap.

FIG. 1 shows an example of non-integer times of bitmap repetition withinthe SFN cycle.

In FIG. 1, the subframes that are indicated with ‘1’ via a bitmaprepresent that they are within the resource pool, and the subframes thatare indicated with ‘0’ via a bitmap represent that they are not withinthe resource pool. The indications of the bitmap are repeated within theSFN cycle. In FIG. 1, the subframes indicated by ‘0’ according to thebitmap may be used by other user equipments or other usages liketransmitting PUSCH.

As shown in FIG. 1, the last bitmap repetition is crossing the DFN/SFNboundary. If a UE (User Equipment) uses this bitmap and reserves theresource as indicated with a numeral reference ‘101’, the reservedresource may collide with the resources of other UEs in a next DFN/SFNcycle as the bitmap is applied from start or certain offset of SFN/DFNcycle.

Based on this consideration, RAN1 of 3GPP agreed to adopt a concept of“reserved subframe”, which should be excluded from the resource poolconfiguration within the SFN/DFN cycle. In this case, the remainingsubframes after excluding the SLSS subframes and the reserved subframescould allow the bitmap repetition with integer times within the SFN/DFNcycle. Still based on the above example that there are 10240 subframeswithin the SFN cycle, the number of the SLSS subframes is 64, and thenumber of the reserved subframes is 76, the number of the remainingsubframes for the resource pool is 10240−64−76=10100, which could bedivided by a 100-bit bitmap. In this case, the collision problemdescribed by FIG. 1 can be solved.

FIG. 2 shows an example that a subframe is reserved within the SFN/DFNcycle presented in the R1-1609726 (a meeting disclosure of RAN1).

As shown in FIG. 2, a subframe 503 is a reserved subframe and should beexcluded for the resource pool. In addition, subframes 255, 256, 257,512, 513 and 514 are used to transmit the SLSS signals and should beexcluded for the resource pool as well.

SUMMARY OF THE DISCLOSURE

Based on the above background art, the problem is how to set or indicatethe reserved subframes within the SFN/DFN cycle. Therefore, the presentdisclosure is made in consideration of the above aspects.

According to one aspect of the present disclosure, there is provided amethod of setting reserved subframes for indication of a resource poolby a bitmap. In the present disclosure, the resource pool is used fortransmitting or receiving sidelink signals within a system frame numbercycle that includes predefined subframes and remaining subframes thatare subframes after excluding the predefined subframes within the systemframe number cycle. In the method, a number of the reserved subframes isdetermined so that the bitmap is repeated by integer times within thesubframes after excluding the reserved subframes and the predefinedsubframes within the system frame number cycle. In the method, positionof each of the reserved subframes is set, wherein at most two reservedsubframes are set per n subframes within the system frame number cycle.

According to another aspect of the present disclosure, there is provideda user equipment for setting reserved subframes for indication of aresource pool by a bitmap. In the present disclosure, the resource poolis used for transmitting or receiving sidelink signals within a systemframe number cycle that includes predefined subframes and remainingsubframes that are subframes after excluding the predefined subframeswithin the system frame number cycle. The user equipment comprises acommunication unit and a subframe reservation unit. The communicationunit is configured to transmit and/or receive sidelink signals. Thesubframe reservation unit is configured to set the reserved subframes,wherein a number of the reserved subframes is determined so that thebitmap is repeated by integer times within the subframes after excludingthe reserved subframes and the predefined subframes within the systemframe number cycle, and at most two reserved subframes are set per nsubframes within the system frame number cycle.

According to a further aspect of the present disclosure, there isprovided a base station for setting reserved subframes for indication ofa resource pool by a bitmap. In the present disclosure, the resourcepool is used for transmitting or receiving sidelink signals within asystem frame number cycle that includes predefined subframes andremaining subframes that are subframes after excluding the predefinedsubframes within the system frame number cycle. The base stationcomprises a communication unit and a subframe reservation unit. Thecommunication unit is configured to transmit and/or receive sidelinksignals. The subframe reservation unit is configured to set the reservedsubframes, wherein a number of the reserved subframes is determined sothat the bitmap is repeated by integer times within the subframes afterexcluding the reserved subframes and the predefined subframes within thesystem frame number cycle, and at most two reserved subframes are setper n subframes within the system frame number cycle.

The method, user equipment, and base station of the present disclosurecould realize the advantages that the resource waste and sidelinktransmission latency in the communication system are minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the present disclosure willbecome more clear and easier to be understood in detailed description ofembodiments of the present disclosure below in conjunction with attacheddrawings, in which:

FIG. 1 shows an example of non-integer times of bitmap repetition withinthe SFN cycle;

FIG. 2 shows an example that a subframe is reserved within the SFN/DFNcycle presented in the R1-1609726 (a meeting disclosure of RAN1);

FIG. 3 shows a flowchart of the method of setting the reserved subframesfor the resource pool according to one embodiment of the presentdisclosure;

FIG. 4 shows an example of the method of setting the reserved subframesfor the resource pool according to one embodiment of the presentdisclosure;

FIG. 5 shows another example of the method of setting the reservedsubframes for the resource pool according to one embodiment of thepresent disclosure;

FIG. 6 shows a further example of the method of setting the reservedsubframes for the resource pool according to one embodiment of thepresent disclosure;

FIG. 7 shows an example of a user equipment for communication by use ofthe resource pool according to one embodiment of the present disclosure;

FIG. 8 shows an example of a base station for communication by use ofthe resource pool according to one embodiment of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the present disclosure. Inthe drawings, similar symbols typically indicate similar components,unless the context dictates otherwise. It will be readily understoodthat aspects of the present disclosure can be arranged, substituted,combined, and designed in a wide variety of different configurations,all of which are explicitly contemplated and make a part of the presentdisclosure.

FIG. 3 shows a method of setting the reserved subframes according to oneembodiment of the present disclosure.

The method as shown in FIG. 3 is performed in a V2V (Vehicle tovehicle)/V2X (vehicle to everything) communication system. In theV2V/V2X communication system, the resource pool is used for transmittingand/or receiving sidelink signals within a system frame number (SFN/DFN)cycle. DFN is Direct Frame Number which could refer to 3GPP TS 36.331.It is a cycle which consists of uplink subframes. In FDD, SFN cycle isbasically the same as DFN cycle, but in TDD, SFN cycle will include allof downlink subframe, special subframe and uplink subframes. Theproposed methods could be used for both SFN cycle and DFN cycle, but fordescription simplicity, SFN is mainly assumed in the following examples.

The system frame number (SFN) cycle includes predefined subframes andremaining subframes. The remaining subframes are subframes afterexcluding the predefined subframes within the system frame number cycle.In the present disclosure, a bitmap indicates whether or not a subframeis a V2V/V2X resource. In the present disclosure, the terms “predefinedsubframe” and “excluded subframe” have the same meaning in the context.The method as shown in FIG. 3 can be executed in either a user equipmentside or a base station side.

As shown in FIG. 3, the method of setting the reserved subframes forindication of a resource pool according to one embodiment of the presentdisclosure comprises of a step S301 and a step S302. In the step S301, anumber of the reserved subframes is determined so that the bitmap isrepeated by integer times within the subframes after excluding thereserved subframes and the predefined subframes within the system framenumber cycle. In the step S302, a position of each of the reservedsubframes is set, wherein at most two reserved subframes are set per nsubframes within the system frame number cycle.

According to an embodiment of the present disclosure, the number of thereserved subframes can be determined based on the size of the bitmap andthe number of the remaining subframes within the system frame numbercycle. For example, the number of the reserved subframes equals to theoperation of (the number of the remaining subframes) mod (the bitmapsize). Specifically, the number ‘Y’ of the reserved subframes can bedetermined based on the following formula: X=(a number of the totalsubframes within a system frame number cycle−a number of the predefinedsubframes within a system frame number cycle), and Y=X mod (the bitmapsize).

FIG. 4 shows an example of the method of setting the reserved subframesaccording to one embodiment of the present disclosure.

In the FIG. 4, each subframe is transmitted in a time of 1 ms. In FIG.4, the blank blocks represent the excluded subframes such as SLSSsubframes, and the blocks with oblique lines represent the reservedsubframes.

As stated above, based on the agreement, the subframes transmittingsidelink synchronization signal (SLSS) should be excluded for theresource pool. In the following context, the subframes that should beexcluded is referred to as “excluded subframes” or “predefinedsubframes”. In the example as shown in FIG. 4, it is assumed that thereare 10240 subframes within a system frame number (SFN) cycle, and eachSLSS subframe is transmitted per 160 ms so there are 64 SLSS subframeswithin the SFN cycle. The number of the remaining subframes after theexcluded subframes are excluded are 10240−64=10176.

For a bitmap with a size of 16 bits, the number of the reserved subframeis 0 as the calculation (10176 mod 16) equals to 0. For a bitmap with asize of 20 bits, the number of the reserved subframe is 16 as thecalculation (10176 mod 20) equals to 16. For a bitmap with a size of 100bits, the number of the reserved subframe is 76 as the calculation(10176 mod 100) equals to 76.

According to an embodiment of the present disclosure, the ‘n’ subframesare determined based on subframe index that is continuous within thesystem frame number cycle. For example, the subframe index can be thesubframe order number such as SF #0, SF #1, SF #2, SF #3, . . . , SF#10240 as shown in FIG. 4, which are continuous within the system framenumber cycle. In this case, the above ‘n subframes’ include both of theremaining subframes and the predefined subframes such as SLSS subframes.That is, the reserved subframes are set per ‘n subframes’ no matterwhether or not the predefined subframes are contained in the ‘nsubframes’.

In this situation, the position of a reserved subframe may overlap withany of the predefined subframes which should be excluded for indicationof the resource pool within the system frame number cycle. In this case,the reserved subframe should be set in a subframe closest to and beforeor after the predefined subframe within the remaining subframes.

According to an embodiment of the present disclosure, as shown in FIG.4, it can be assumed that n=100, i.e., one subframe can be reserved per100 subframes (as indicated as HFN). According to another embodiment,the “100 subframes” can be counted from the start of system frame numbercycle (in this example, the number of subframe offset is assumed aszero). In an example that there is a subframe offset within the SFNcycle, the “100 subframes” can be counted from the end of the subframeoffset within system frame number cycle.

In this case, for a bitmap with a size of 20 bits, the number of thereserved subframe is 16, so the reserved subframes can be from HFN #0 toHFN #15. For a bitmap with a size of 100 bits, the number of thereserved subframe is 76, so the reserved subframes can be from HFN #0 toHFN #75.

According to another example, the “100 subframes” are not necessary tobe counted from the start of the system frame number cycle, the “100subframes” can be counted from any position of the system frame numbercycle. For example, In the case of a bitmap with a size of 20 bits, thenumber of the reserved subframe is 16, the “100 subframes” can be fromHFN #10 to HFN #25, or from HFN #84 to HFN #99, etc. In the case of abitmap with a size of 100 bits, the number of the reserved subframe is76, the “100 subframes” can be from HFN #0 to HFN #75, or from HFN #10to HFN #85, or from HFN #24 to HFN #99, etc.

For the embodiment that n=100, the benefit is that it is a simplesolution from standardization point of view, and it can be used for anycase considering that a maximum number of subframes after mod operationis 99. Also as the position of the reserved subframe is somehow common,different resource pool configurations may be related with the samereserved subframes so that resource utilization is improved.

According to another example of the present embodiment, the n subframescan be determined based on the remaining subframes within the systemframe number cycle. That means that the above ‘n subframes’ do notinclude the predefined subframes. That is, the reserved subframes areset per ‘n subframes’ in which the ‘n subframes’ are n remainingsubframes available for the resource pool that do not contain thepredefined subframes.

According to an example of the present embodiment, the number ‘n’ equalsto the operation of FLOOR (the number of the remaining subframes/thenumber of the reserved subframes)”, where FLOOR is the operation ofround down to the nearest integer. Specifically, the number ‘n’ can bedetermined based on the following formula:X=(a number of the total subframes within a system frame number cycle−anumber of the predefined subframes within a system frame number cycle)Y=X mod(bitmap size)n=FLOOR(X/Y)where FLOOR is the operation of round down to the nearest integer.

According to another embodiment of the present disclosure, the number‘n’ could be configured or preconfigured.

According to another example of the embodiment, a reserved subframe andan excluded subframe such as the SLSS subframe can not overlap. If theirpositions overlap, the reserved subframe should be placed in a subframebefore or after the excluded subframe that is overlapped.

FIG. 5 shows another example of the method of setting the reservedsubframes according to one embodiment of the present disclosure.

In FIG. 5, the blank blocks represent the predefined subframes such asthe SLSS subframes, and the blocks with oblique lines represent thereserved subframes.

In this example, it is also assumed that there are 10240 subframeswithin a SFN cycle, and 64 SLSS subframes are excluded for V2X resourcepool in which 160 ms periodicity of a SLSS subframe is assumed so thatthe remaining subframes are 10240−64=10176 subframes.

In the example as shown in FIG. 5, each of the reserved subframes is setat middle of two predefined subframes such as the SLSS subframes thatare adjacent to each other. In this case, since each SLSS subframe istransmitted in a period of 160 ms periodicity, one or two reservedsubframes are set per 160 subframes within the system frame numbercycle.

Specifically, for a bitmap with a size of 16 bits, the number of thereserved subframe is 0. For a bitmap with a size of 20, the number ofthe reserved subframe is 16, and one reserved subframe can be set atmiddle of two SLSS subframes from start or other positions of the SFNcycle.

However, for a bitmap with a size of 100 bits, the number of thereserved subframe is 76. In this case, if only one reserved subframe isset at middle of two adjacent predefined subframes such as the SLSSsubframes, there are 13 reserved subframes left nowhere to be set.According to another example of the present disclosure, a pair of tworeserved subframes will be set at middle of two predefined subframessuch as the SLSS subframes. The number of “2” reserved subframes betweenthe same two predefined subframes such as the SLSS subframes is76−63=13, and the number of ‘1’ reserved subframes is 63. The patternsetting the reserved subframes may be like {2 2 2 . . . 1 1 1 . . . 1 11}, or {1 1 1 . . . 2 2 2 . . . 1 1 1}, or {1 1 1 . . . 1 1 1 . . . 2 22}, {2 2 2 . . . 2 2 2 . . . 1 1 1}, or {1 1 1 . . . 2 2 2 . . . 2 2 2},or {2 2 2 . . . 1 1 1 . . . 2 2 2}, or {2 2 2 . . . 2 2 2 . . . 2 2 2},or others. The above pattern means that the “2” reserved subframesbetween the same two predefined subframes such as the SLSS subframes canbe placed at any position within the SFN cycle.

The benefit of such an embodiment is that all the predefined subframesand the reserved subframes for the resource pool are distributed as muchas possible and it minimizes the latency of the sidelink signaltransmission.

FIG. 6 shows a further example of the method of setting the reservedsubframes according to one embodiment of the present disclosure.

In this example, it is also assumed that there are 10240 subframeswithin a SFN cycle, 64 SLSS subframes are excluded for V2X resourcepool, and the periodicity of a SLSS subframe is assumed as 160 ms, soV2X resource pool has 10240−64=10176 subframes.

As stated above, the number ‘n’ can be determined based on the followingformula:X=(a number of the total subframes within a system frame number cycle−anumber of the predefined subframes within a system frame number cycle)Y=X mod(bitmap size)n=FLOOR(X/Y)where FLOOR is the operation of round down to the nearest integer.

Based on the above formula, for a bitmap with a size of 100 bits,X=10176, Y=10176 mod 100=76, n=floor (10176/76)=133. Therefore, onereserved subframe can be set per 133 subframes within the SFN cycle, andtotally there are 76 reserved subframes. In this case, the bitmap with100 bits could be repeated by integer times within the SFN cycle. For abitmap with a size of 16 bits and a bitmap with a size of 20 bits, thesame procedure could be carried out.

According to another example of the present embodiment, in addition tothe sidelink synchronization subframes (SLSS), the predefined subframescan further include downlink subframes and special subframes in TDD, andsubframes indicated by a subframe offset with the first system framenumber (SFN #0) within the system frame number cycle. That is, thepredefined subframes include at least one of the downlink subframes andthe special subframes in TDD, the sidelink synchronization subframes,and the subframes indicated by a subframe offset with the start of thesystem frame number cycle. In a special case for example for FDD, thesubframe offset could be set to zero.

Specifically, in case of TDD where there are downlink (DL) subframes,special subframes and uplink (UL) subframes, the DL subframes and thespecial subframes as well as the SLSS subframes should be excluded forthe resource pool. For example, for TDD configuration 0, there are only1024 uplink subframes within a SFN cycle, and these 1024 uplinksubframes are potential subframes for V2X resource pool. Assuming thenumber of the SLSS subframes is 64, the remaining subframes are1024−64=960 subframes for V2X resource pool. Based on the above formula,X=960, Y=(960 mod 100)=60, n=FLOOR (960/60)=16. It means that onereserved subframe is set per 16 uplink subframes.

FIG. 7 shows an example of the user equipment for setting reservedsubframes according to one embodiment of the present disclosure.

In the user equipment as shown in FIG. 7, the resource pool is used fortransmitting and/or receiving sidelink signals within a system framenumber cycle. The system frame number cycle includes predefinedsubframes and remaining subframes. The remaining subframes are subframesafter excluding the predefined subframes within the system frame numbercycle. A bitmap indicates whether or not a subframe is a V2V/V2Xresource.

As shown in FIG. 7, the user equipment 700 according to the embodimentof the present disclosure includes a communication unit 701, a subframereservation unit 702, a microprocessor unit 703, and a memory unit 704.The above respective units are interconnected by use of data and/orcontrol bus within the user equipment 700.

According to an embodiment of the present disclosure, the user equipment700 is configured to communicate with other user equipments or basestations by use of a resource pool.

The communication unit 701 is configured to transmit sidelink signals toother user equipments or base stations and/or receive sidelink signalsfrom the other user equipments or base stations by use of V2V (vehicleto vehicle)/V2X (vehicle to everything) resource pool in thecommunication system. The communication unit 701 may further compriseother hardware such as a baseband processor and a radio frequencymodulation unit for processing and/or modulating the signals to betransmitted in the communication system.

The subframe reservation unit 702 is configured to set reservedsubframes, wherein a number of the reserved subframes is determined sothat the bitmap is repeated by integer times within the subframes afterexcluding the reserved subframes and the predefined subframes within thesystem frame number cycle, and at most two reserved subframes are setper n subframes within the system frame number cycle.

The microprocessor unit 703 is configured to execute related programs toprocess various data stored in the memory unit 704, and controloperations of respective units in the user equipment 700.

The memory unit 704 may further include a ROM (Read Only Memory) and aRAM (Random Access Memory) which are not shown in the Figure. The ROM isconfigured to store various programs required for performing variousprocesses and controls by the microprocessor 703, and the RAM isconfigured to store intermediate data temporarily produced in theprocedure of the processes and controls by the microprocessor unit 703.

According to one embodiment of the present disclosure, the userequipment 700 may further comprise an antenna unit. The antenna unit isconfigured to transmit and/or receive signals to and/or from other userequipments or base stations.

According to one embodiment of the present disclosure, the userequipment 700 may further comprise an interface unit. The interface unitmay be but not limited to one type of USB, IEEE13954, RJ11, RJ45, etc.The interface unit is configured to connect with user's externaldevices, such as but not limited to a computer device, a keyboard, or amouse, and receive control information and/or program command from theuser and/or output data to the user's external devices.

Respective devices and/or units as described above do not limit thescope of the present disclosure, and the user equipment 700 of thepresent disclosure may include more or less devices and/or units.

According to another embodiment of the present disclosure, the number ofthe reserved subframes is determined based on the size of the bitmap andthe number of the remaining subframes within the system frame numbercycle.

According to another embodiment of the present disclosure, the number ofthe reserved subframes equals to the operation of (the number of theremaining subframes) mod (the bitmap size).

According to another embodiment of the present disclosure, each of thereserved subframes is set at middle of the adjacent predefinedsubframes.

According to another embodiment of the present disclosure, the nsubframes are based on subframe index that is continuous within thesystem frame number cycle.

According to another embodiment of the present disclosure, if theposition of the reserved subframe overlaps with any of the predefinedsubframe that should be excluded for indication of the resource poolwithin the system frame number cycle, the reserved subframe is set in aclosest subframe before or after the predefined subframe withinremaining subframes.

According to another embodiment of the present disclosure, the number‘n’ is at least 100.

According to another embodiment of the present disclosure, the nsubframes are based on the remaining subframes within the system framenumber cycle.

According to another embodiment of the present disclosure, the number nequals to the operation of FLOOR (the number of the remainingsubframes/the number of the reserved subframes)”, where FLOOR is theoperation of round down to the nearest integer.

According to another embodiment of the present disclosure, thepredefined subframes include at least one of downlink subframes andspecial subframes in TDD, sidelink synchronization subframes, andsubframes indicated by a subframe offset with the start of system framenumber within the system frame number cycle.

FIG. 8 shows an example of the base station for setting reservedsubframes according to one embodiment of the present disclosure.

In the base station as shown in FIG. 8, the resource pool is used fortransmitting and/or receiving sidelink signals within a system framenumber cycle. The system frame number cycle includes predefinedsubframes and remaining subframes. The remaining subframes are subframesafter excluding the predefined subframes within the system frame numbercycle. A bitmap indicates whether or not a subframe is a V2V/V2Xresource.

As shown in FIG. 8, the base station 800 according to the embodiment ofthe present disclosure includes a communication unit 801, a subframereservation unit 802, a microprocessor unit 803, and a memory unit 804.The above respective units are interconnected by use of data and/orcontrol bus within the base station 800.

According to an embodiment of the present disclosure, the base station800 is configured to communicate with other base stations or userequipments by use of the resource pool.

The communication unit 801 is configured to transmit sidelink signals toother base stations or user equipments and/or receive sidelink signalsfrom the other base stations or user equipments by use of V2V (vehicleto vehicle)/V2X (vehicle to everything) resource pool in thecommunication system. The communication unit 801 may further compriseother hardware such as a baseband processor and a radio frequencymodulation unit for processing and/or modulating the signals to betransmitted in the communication system.

The subframe reservation unit 802 is configured to set reservedsubframes, wherein the number of the reserved subframes is determined sothat the bitmap is repeated by integer times within the subframes afterexcluding the reserved subframes and the predefined subframes within thesystem frame number cycle, and at most two reserved subframes are setper n subframes within the system frame number cycle.

The microprocessor unit 803 is configured to execute related programs toprocess various data stored in the memory unit 804, and controloperations of respective units in the base station 800.

The memory unit 804 may further include a ROM (Read Only Memory) and aRAM (Random Access Memory) which are not shown in the Figure. The ROM isconfigured to store various programs required for performing variousprocesses and controls by the microprocessor 803, and the RAM isconfigured to store intermediate data temporarily produced in theprocedure of the processes and controls by the microprocessor unit 803.

According to one embodiment of the present disclosure, the base station800 may further comprise an antenna unit. The antenna unit is configuredto transmit and/or receive sidelink signals to and/or from other basestations or user equipments.

According to one embodiment of the present disclosure, the base station800 may further comprise an interface unit. The interface unit may bebut not limited to one type of USB, IEEE13954, RJ11, RJ45, etc. Theinterface unit is configured to connect with user's external devices,such as but not limited to a computer device, a keyboard, or a mouse,and receive control information and/or program command from the userand/or output data to the user's external devices.

Respective devices and/or units as described above do not limit thescope of the present disclosure, and the base station 800 of the presentdisclosure may include more or less devices and/or units.

According to another embodiment of the present disclosure, the number ofthe reserved subframes is determined based on the size of the bitmap andthe number of the remaining subframes within the system frame numbercycle.

According to another embodiment of the present disclosure, the number ofthe reserved subframes equals to the operation of (the number of theremaining subframes) mod (the bitmap size).

According to another embodiment of the present disclosure, each of thereserved subframes is set at middle of the adjacent predefinedsubframes.

According to another embodiment of the present disclosure, the nsubframes are based on subframe index that is continuous within thesystem frame number cycle.

According to another embodiment of the present disclosure, if theposition of the reserved subframe overlaps with any of the predefinedsubframe that should be excluded for indication of the resource poolwithin the system frame number cycle, the reserved subframe is set in aclosest subframe before or after the predefined subframe withinremaining subframes.

According to another embodiment of the present disclosure, the number‘n’ is at least 100.

According to another embodiment of the present disclosure, the nsubframes are based on the remaining subframes within the system framenumber cycle.

According to another embodiment of the present disclosure, the number‘n’ equals to the operation of FLOOR (the number of the remainingsubframes/the number of the reserved subframes)”, where FLOOR is theoperation of round down to the nearest integer.

According to another embodiment of the present disclosure, thepredefined subframes include at least one of downlink subframes andspecial subframes in TDD, sidelink synchronization subframes, andsubframes indicated by a subframe offset with the start of system framenumber within the system frame number cycle.

The above embodiments of the present disclosure are only exemplarydescription, and their specific structures and operations do not limitthe scope of the present disclosure. Those skilled in the art canrecombine different parts and operations of the above respectiveembodiments to produce new implementations which equally accord with theconcept of the present disclosure.

The embodiments of the present disclosure may be implemented byhardware, software and firmware or in a combination thereof, and the wayof implementation does not limit the scope of the present disclosure.

The connection relationships between the respective functional elements(units) in the embodiments of the present disclosure do not limit thescope of the present disclosure, in which one or multiple functionalelement(s) or unit(s) may contain in or be connected to any otherfunctional elements.

Although several embodiments of the present disclosure has been shownand described in combination with attached drawings above, those skilledin the art would understand that variations and modifications whichstill fall into the scope of claims and their equivalents of the presentdisclosure can be made to these embodiments without departing from theprinciple and spirit of the present disclosure.

What is claimed is:
 1. A communication apparatus, comprising: circuitrywhich, in operation, determines a first set of subframes available for asidelink operation; and a transmitter which, in operation, transmits asidelink signal in a subframe among the first set of subframes, whereinthe first set of subframes is formed of 10240 subframes minus a secondset of subframes and minus reserved subframes, the second set ofsubframes including subframes for transmitting a sidelinksynchronization signal (SLSS), and the reserved subframes beingdetermined based on a length of a bitmap configured for the first set ofsubframes, and wherein a number of the reserved subframes (Y) within the10240 subframes is determined by:Y=X mod (the length of the bitmap),where X=10240−(a number of subframes in the second set of subframes). 2.The communication apparatus according to claim 1, wherein, intervalsbetween the reserved subframes are determined based on the length of thebitmap and the number of subframes in the second set of subframes. 3.The communication apparatus according to claim 1, wherein, the reservedsubframes are set per n subframes, within the 10240 subframes minus thesecond set of subframes, n being determined by a following formula:n=FLOOR (X/Y) where FLOOR is the operation of round down to the nearestinteger.
 4. The communication apparatus according to claim 1, wherein, anumber “n” of subframes, for which at most two of the reserved subframesare set, is at least
 100. 5. The communication apparatus according toclaim 1, wherein, the second set of subframes includes at least onesubframe chosen from downlink subframes and special subframes in TDD. 6.The communication apparatus according to claim 1, wherein, each bit ofthe bitmap indicates whether each corresponding subframe is a subframeused for the sidelink operation.
 7. The communication apparatusaccording to claim 1, wherein, the bitmap is repeated within the firstset of subframes.
 8. A communication method comprising: determining afirst set of subframes available for a sidelink operation; andtransmitting a sidelink signal in a subframe among the first set ofsubframes, wherein the first set of subframes is formed of 10240subframes minus a second set of subframes and minus reserved subframes,the second set of subframes including subframes for transmitting asidelink synchronization signal (SLSS), and the reserved subframes beingdetermined based on a length of a bitmap configured for the first set ofsubframes, and wherein a number of the reserved subframes (Y) within the10240 subframes is determined by:Y=X mod (the length of the bitmap),where X=10240−(a number of subframes in the second set of subframes). 9.The communication method according to claim 8, wherein, the reservedsubframes are set per n subframes, within the 10240 subframes minus thesecond set of subframes, n being determined by a following formula:n=FLOOR (X/Y), where FLOOR is the operation of round down to the nearestinteger.
 10. A communication apparatus, comprising: circuitry which, inoperation, determines a first set of subframes available for a sidelinkoperation; and a transmitter which, in operation, transmits a sidelinksignal in a subframe among the first set of subframes, wherein the firstset of subframes is formed of 10240 subframes minus a second set ofsubframes and minus reserved subframes, the second set of subframesincluding subframes for transmitting a sidelink synchronization signal(SLSS), and the reserved subframes being determined based on a length ofa bitmap configured for the first set of subframes, and wherein a numberof the reserved subframes (Y) within the 10240 subframes is determinedby:Y=X mod (the length of the bitmap),where X=10240−(a number of subframes in the second set of subframes),wherein the reserved subframes are set per n subframes, within the 10240subframes minus the second set of subframes, the n subframes notcontaining the second set, and n being determined by a followingformula:n=FLOOR (X/Y), where FLOOR is the operation of round down to the nearestinteger.
 11. A communication method comprising: determining a first setof subframes available for a sidelink operation; and transmitting asidelink signal in a subframe among the first set of subframes, wherein,the first set of subframes is formed of 10240 subframes minus a secondset of subframes and minus reserved subframes, the second set ofsubframes including subframes for transmitting a sidelinksynchronization signal (SLSS), and the reserved subframes beingdetermined based on a length of a bitmap configured for the first set ofsubframes, and wherein a number of the reserved subframes (Y) within the10240 subframes is determined by:Y=X mod (the length of the bitmap),where X=10240−(a number of subframes in the second set of subframes),and wherein the reserved subframes are set per n subframes, within the10240 subframes minus the second set of subframes, the n subframes notcontaining the second set, and n being determined by a followingformula:n=FLOOR (X/Y), where FLOOR is the operation of round down to the nearestinteger.